Let’s see what’s going on here! The transmission fluid has never been changed, right? You don’t say how many miles are on the F-150, however, since it’s an 07 and if it has been driven an average of 12,000 miles per year or so, it likely has about 100,000 miles on it.
There’s a problem staring at you, right away. Transmission fluid should be replaced at between 30,000 and 50,000 miles (I know there are some supposed 100,000-mile fluid settings but I don’t think it should ever wait that long). And, assuming there’s 100,000 miles on the F-150, you should have changed out the transmission fluid at least twice. It’s just not meant to be sitting in the transmission that long.
If it has been there and if it is black, obviously, it has to come out. The best way is to simply drain the transmission and then remove the pan cover to get the last quart out. Never use a flush, especially a pressure flush, to clean the fluid. Though some shops use and advocate a power flush, in my hunble opinion, it just leads to transmission damage. The reason I say this is simple: when you attach the high-pressure line to one side of the transmission and apply air pressure, all you are doing is blowing everything out of the transmission.
It does clean everything out, including hardened deposits which will break off and rip through other parts of the transmission, causing damage. At the very least, it is possible with a high-pressure flush to see not only torque converter damage but also impeller damage as well as trouble with the gears and bands/clutches. It is even possible to have check-valve damage in the valve body as the small valves plug up with pressure-driven gunk.
That’s why I recommend the more labor-intensive draining, it is better for the transmission, all around.
Next, swap out the transmission filter so you can be sure you are starting off as cleanly as possible when you add in the new transmission fluid. Now, add in the right amount of transmission fluid — check the owner’s manual. Things should work better when you have completed this.
I am not saying you won’t have further problems. After all, you said nothing has been done to the transmission fluid and it is dark, which indicates that there is very little capability left to it. I am saying that changing the transmission fluid is the normal first step to see if there might be more damage (I suspect there is).
If you are very lucky — and my hunch is wrong — you won’t have further problems with the F-150 once you’ve swapped out the fluid and everything will work correctly. However, you have to remember that the new transmission fluid is also detergent in nature and any buildups will break loose and they may also cause damage. The reason broken off materials can cause damage is that they are usually rock-hard and can easily either lodge in sensitive parts like the check valves or they can actually harm things like turbine blades, further upsetting things.
I think you are right in keeping the other unit — I am assuming the other unit you are referring to is a transmission — because the potential for problems in the first, honestly abused tranny are likely too great to fix. I am only advocating the new fluid in the first transmission to see if there is any possibility it can be used. If it can, then you are ahead of the game, if not, you have a backup to swap in quickly at a cost of about $1,200 in labor or so.
One last question, what was the transmission error code?
